Liquid crystalline bis-chlorocarbonic acid esters

ABSTRACT

Liquid crystalline bis-chlorocarbonic acid esters are 4-hydroxybenzoic acid-(4&#39;-hydroxyphenyl) esters corresponding to the following formula ##STR1## wherein R 1 , R 2 , R 3  and R 4  denote, independently of one another, hydrogen, a halogen atom or a C 1  to C 6  alkyl group. Preparation of (I) and liquid crystalline N-alkyl polyurethanes and polycarbonates prepared from (I) are other invention embodiments.

This is a division of application Ser. No. 315,859 filed Feb. 27, 1989now U.S. Pat. No. 4,980,441.

This invention relates to new liquid crystalline bis-chlorocarbonic acidesters of 4-hydroxyphenyl esters of 4-hydroxybenzoic acids, theirpreparation and the liquid crystalline N-alkyl polyurethanes andpolycarbonates prepared from them.

Bis-chlorocarbonic acid esters of numerous bis-hydroxy compounds arealready known, e.g. the bis-chlorocarbonic acid esters of2,2-bis-(4-hydroxyphenyl)-propane,1,1-bis-(4-hydroxyphenyl)-cyclohexane, bis-(4-hydroxyphenyl)-sulphideand hexahydrofuro(3,2-b)furan-3,6-diols (see e.g. Makromol. Chem. 571-11, 1962 and EP-B-0 025 937).

It has now been found that bis-chlorocarbonic acid esters which arederived from 4-hydroxyphenyl esters of 4-hydroxybenzoic acids haveparticularly advantageous properties. It was found that thesebis-chlorocarbonic acid esters are in themselves liquid crystallinecompounds and that they transfer this property to the N-alkylpolyurethanes and polycarbonates prepared from them by a reaction withdisecondary diamines or dihydroxy compounds.

These N-alkyl polyurethanes obtainable from bis-chlorocarbonic acidesters of 4-hydroxybenzoic-acid-(4'-hydroxyphenyl) esters not only havethe advantages of N-alkyl polyurethanes such as high heat resistance butthanks to their LC properties they also have improved flow properties inthe melt and are therefore more easily processed, in particular to formthin walled moulded parts. They also have increased dimensionalstability under heat and an increased modulus of elasticity as well asexcellent chemical resistance, high flame resistance and goodcompatability for fillers. The same also applies to the polycarbonatesobtainable from the bis-chlorocarbonic acid esters of 4-hydroxybenzoicacid-(4'-hydroxyphenyl)-esters.

The properties described above of N-alkyl polyurethanes andpolycarbonates obtainable from bis-chlorocarbonic acid esters of4-hydroxybenzoic acid-(4'-hydroxyphenyl)-esters are of great practicalimportance for polyurethanes and polycarbonates which are to be used formoulded parts which are to be subjected to severe mechanical and thermalstresses. The polyurethanes and polycarbonates obtainable from the saidchlorocarbonic acid esters provide the possibility of obtaining polymerssuitable for fields of application for which synthetic resins have nothitherto been usable.

This invention therefore relates to bis-chlorocarbonic acid esters of4-hydroxybenzoic acid-(4'-hydroxyphenyl) esters corresponding to thefollowing formula ##STR2## wherein

R₁, R₂, R₃ and R₄ denote, independently of one another, hydrogen, ahalogen atom, preferably a chlorine or bromine atom, or a C₁ to C₆ alkylgroup, preferably a C₁ to C₄ alkyl group.

The invention further relates to a process for the preparation of thebis-chlorocarbonic acid esters of Formula (I). In the process4-hydroxybenzoic acid-(4'-hydroxyphenyl) esters corresponding to thefollowing formula ##STR3## in which

R₁, R₂, R₃ and R₄ have the meanings given for Formula (I) are reactedwith phosgene in the presence of acid binding agents by the method knownfor the reaction of phosgene with phenols.

The reaction may be carried out in organic solvents which are immisciblewith water and inert under the reaction conditions, such as toluene ormethylene chloride, using acid binding agents which are insoluble inthese solvents, e.g. organic bases such as dimethyl aniline, or usingacid binding agents which are insoluble in or immiscible with thesesolvents, such as NaHCO₃ or aqueous sodium hydroxide solution. It issurprisingly found that although 4-hydroxybenzoicacid-(4'-hydroxyphenyl) esters of Formula (II) are not liquidcrystalline compounds, their reaction with phosgene gives rise tobis-chlorocarbonic acid esters which have LC properties.

The 4-hydroxybenzoic acid-(4'-hydroxyphenyl) esters of Formula (II)required as starting compounds for the preparation of thebis-chlorocarbonic acid esters according to the invention of Formula (I)and the preparation of these esters of Formula (II) are described inDE-OS 3 622 611 or may be obtained by methods described in the saidpublication.

The invention further relates to the polyurethanes and polycarbonatesobtained from the reaction of the liquid crystalline bis-chlorocarbonicacid esters of Formula (I) with disecondary diamines or dihydroxycompounds corresponding to the following formula

    HX--A--XH                                                  (III)

in which

X stands for oxygen or a N(R) group wherein

R denotes a C₁ to C₄ alkyl group, preferably a methyl group, or togetherwith R of the second N(R) group forms an ethylene group optionallysubstituted by a C₁ to C₄ alkyl group and

A denotes a divalent residue of an aliphatic hydrocarbon, preferably anα,ω-alkylene residue, optionally interrupted by oxygen and/or siliconatoms and/or by a N(C₁ -C₄ alkyl) group, or the divalent residue of anaromatic hydrocarbon, under the condition that A has an averagemolecular weight M below 600, preferably from 28 to 600.

The polyurethanes and polycarbonates according to the invention containstructural units corresponding to the following formula ##STR4## wherein

R₁, R₂, R₃ and R₄ have the meanings given for Formula (I) and

X and A have the meanings given for Formula (III).

For the LC properties of the polyurethanes and polycarbonates containingstructural units of Formula (IV), it is essential that the proportion byweight of the structural units corresponding to the following formula##STR5## based on the total weight of the polymers is from 25 to 90% byweight, preferably from 30 to 85% by weight. For obtaining as much aspossible high molecular weights, it is advantageous to use thechlorocarbonic acid esters according to the invention corresponding toFormula (I) and the diamines and dihydroxy compounds corresponding toFormula (III) in a molar ratio of about 1:1.

When mixtures of diamines and dihydroxy compounds of Formula (III) areused, the products obtained are LC polymers which contain both urethaneand carbonate structural units (X=N(R) and O).

The reaction of the bis-chlorocarbonic acid esters according to theinvention corresponding to Formula (I) with the diamines and dihydroxycompounds of Formula (III) is preferably carried out in an organicsolvent which is immiscible with water and inert under the reactionconditions, in the presence of acid binding agents at temperatures offrom -10° to +20° C.

The acid binding agents used may be inorganic bases such as NaHCO₃,organic bases such as triethylamine or mixtures of inorganic and organicbases. Suitable organic solvents which are inert under the reactionconditions are in particular aliphatic chlorinated hydrocarbons such asmethylene chloride and ethylene chloride.

The diphasic system of methylene chloride/water is preferably employed.

After the reaction mixtures have been worked up by separation of theorganic phase, removal of the monomolecular compounds present in theorganic phase by washing with water, drying and removal of the solvent,the polymer is obtained in the form of a transparent solid which has theproperty of a synthetic material.

The divalent groups denoted by A may be aliphatic hydrocarbons in whichthe carbon chain may be interrupted by oxygen and/or silicon atomsand/or by N(alkyl) groups, for example the following: C₂ to C₄ alkylenegroups such as ethylene, propylene-(1,3) and butylene-(1,4); or theresidues of alkylene polyethers and polyamines corresponding to thefollowing formula ##STR6## wherein

R₅ stands for hydrogen or methyl,

X has the meaning indicated for Formula (I) and

x stands for an integer of from 10 to 40; and the residues ofpolysiloxanes corresponding to the following formula ##STR7## wherein

n stands for 0 to 1 and

y stands for an integer of from 5 to 25 when n=0 and for an integer offrom 10 to 40 when n=1.

In view of the requirement that A should have an average molecularweight M of less than 600, preferably from 28 to 600, it is evident thatdisecondary diamines derived from residues of high molecular weightalkylene polyethers and polyamines of Formulae (V) and (VI) anddihydroxy compounds corresponding to Formula (III) may only be used inadmixture with low molecular weight disecondary diamines and/ordihydroxy compounds of Formula (III) and that the proportion of highmolecular weight compounds of Formula (III) in this mixture must be suchthat the molecular weight of A has an average value of from 28 to 600.

The following are examples of divalent residues of aromatic hydrocarbonssuitable as A:

The phenylene-(1,4) and the naphthylene-(1,5) group and groups in whichtwo or more phenylene groups are linked together in the 1,4 position byway of oxygen, sulphur, a sulphone group, a carbonyloxy group or analkylene group. The following are examples of such groups: ##STR8##

The following are examples of compounds of Formula (III): disecondarydiamines (X=N(R)) such as ethylene diamine, propylene diamine,piperazine, 2,5-dimethyl piperazine, N,N'-dimethyl ethylene diamine,N,N',N"-trimethyldiethylene triamine andN,N'-dimethyl-1,5-diaminonaphthalene; dihydroxy compounds (X=0) such asethylene glycol, propylene glycol-(1,2), butane-1,4-diol, polyethyleneand polypropylene glycols containing from 10 to 40 ethylene or propyleneoxide units, and polydimethyl silanols containing from 5 to 25Si(CH₃)--0 units, as well as bisphenols such as those corresponding tothe following formulae: ##STR9##

EXAMPLE 1

150 g of phosgene are slowly introduced at 0° C. into the suspension of100 g of 4-hydroxybenzoic acid-(4-hydroxyphenyl) ester in 500 ml oftoluene. The reaction mixture is cooled to -5° C. and 121 g of dimethylaniline are added dropwise at this temperature. After the reactionmixture has then been left to react for 30 minutes, it is left to coolto room temperature and stirred for 3 hours at this temperature. Afterthe excess phosgene has been blown off with nitrogen, the reactionsolution is washed, first with 10% hydrochloric acid and then severaltimes with distilled water. The solution is dried and freed from thesolvent. The solvent remaining behind is purified by recrystallizationfrom cyclohexane.

118·6 g (=76·8% of the theory) of bis-chlorocarbonic acid ester areobtained in the form of colourless crystals.

M.p.:125° to 128° C.

Clarification point: 120° C. monotropic, liquid crystalline.

EXAMPLE 2

8·27 g of the bis-chlorocarbonic acid ester obtained according toExample 1 are dissolved in 250 ml of methylene chloride. The solution isprecooled to 0° C. and added with vigorous stirring to a solution, alsocooled at 0° C., of 4·8 g of piperazine hexahydrate, 3·11 g of NaHCO₃and 2 g of triethylamine in 250 ml of water. Stirring of the reactionmixture is then continued for 1 hour at 0° C. The organic phase is thenseparated, washed with water until neutral, dried and finally freed fromsolvent. The liquid residue is poured out on an aluminium sheet where itforms a solid, slightly cloudy film with the properties of a syntheticmaterial after the last residues of solvent have evaporated off.Investigation of the film under a polarisation microscope shows that ithas liquid crystalline properties in the temperature range of from 256°to 300° C. The Staudinger Index is 144·5 cm³ /g. The molecular weightdetermined by gel chromatography was found to be 60,000.

EXAMPLE 3

The procedure is the same as described in Example 2 except that amixture of 4·55 g of piperazine hexahydrate and 1·8 g of anα,ω-bis-methylamino-polysiloxane corresponding to the following formula

    CH.sub.3 NH-(CH.sub.2).sub.2 --O--[Si(CH.sub.3).sub.2 --O--].sub.29·5 --(CH.sub.2).sub.2 --NHCH.sub.3

is used instead of 4·8 g of piperazine hexahydrate.

A slightly cloudy, very flexible plastics film is obtained.

Investigation of the film under a polarisation microscope shows that ithas liquid crystalline properties in the range of from 250° to 300° C.The Staudinger Index is 138·5 cm³ /g and the gel chromatographicallydetermined molecular weight is 84,000.

EXAMPLE 4

The procedure is the same as described in Example 2 except that 5·75 gof 4-hydroxybenzoic acid-(4-hydroxyphenyl) ester are used instead of 4·8g of piperazine hexahydrate.

A clear, flexible plastics film is obtained.

Investigation under the polarisation microscope shows that it melts at220° C. and has liquid crystalline properties in the range of from 240°to 350° C.

EXAMPLE 5

The procedure is the same as described in Example 2 except that amixture of 2·43 g of piperazine hexahydrate and 2·88 g of4-hydroxybenzoic acid-(4-hydroxyphenyl) ester is used instead of 4·8 gof piperazine hexahydrate.

A solid, flexible plastics film is obtained.

Investigation under the polarisation microscope shows that the producthas a melting point at 240° C. and liquid crystalline properties in thetemperature range of from 240° C. to 350° C.

EXAMPLE 6

8·27 g of the bis-chlorocarbonic acid ester obtained according toExample 1 are reacted with 4.55 g of piperazine hexahydrate and 3·13 gof an α,ω-bis-(methylamino)-polypropylene glycol under the conditionsdescribed in Example 2 and using 4 g of NaHCO₃ and 2 g of triethylamine.

A solid, highly flexible and elastic plastics film is obtained.

Investigation under the polarisation microscope shows that the producthas a melting point of 160° C. and liquid crystalline properties in thetemperature range of from 210° to 335° C.

We claim:
 1. Bis-chlorocarbonic acid esters of 4-hydroxybenzoicacid-(4'-hydroxyphenyl)-esters corresponding to the following formula##STR10## wherein R₁, R₂, R₃ and R₄ denote, independently of oneanother, hydrogen, a halogen atom of a C₁ to C₆ alkyl group.